Arthur m



Patented Feb. 26, 1929.

UNITED STATES PATENT OFFICE.

ARTHUR M. HOWALD, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR- TO THE GRASSELLI CHEMICAL COMPANY, OF CLEVELAND, OHIO, A CORPORATION OF OHIO.

WOOD IMPREGNATION.

N Drawing.

This invention relates to the preservation of wood by the impregnation thereof with oily wood preserving agents. More particularly, it relates to the treatment of oily woodin'ipregnating materials or mixtures for the purpose of improving their penetrative powers thus shortening and making more easy the process of impregnating wood with same.

As is well known, wood is preserved by impregnating same with petroleum oils, coal tar oils, wood tar oils, mixtures of these, and the like. In the preservation of wood with these oily agents a thorough penetration is desired for which purpose seasoning or drying of the wood, steaming of the wood, and during the impregnation, vacuum, pressure, and high temperatures are resorted to.

The present invention relates to the treatment of impregnating oils whereby they are rendered more penetrative and the ease of injecting them into wood for thorough pene tration is thereby greatly increased.

It has been found that if oily wood impregnating agents, regardless of their viscosity, be treated with acids, their ease of injection into Wood is materially increased and the time, pressure, and temperature required to obtain a given impregnation may be corresponding ly decreased. Also if the usual conditions of treatment are adhered to a greater depth and completeness of penetration and corresponding preservative effect may be obtained.

In practicing this invention the oily impregnating agent, preferably warmed, is agitated with the acid (a 30 per cent solution or other convenient strength of sulfuric acid may be used), after which the mixture is al lowed to stand, the acid settles out, and may be used for treating additional quantities of impregnating oil.

Any convenient strength of sulfuric, 11y- (lrochloric, phosphoric or other acid, or acid salt such as niter cake, waste acids from petroleum refining, etc., may be used. A convenient method of practicing this invention is to add to the hot impregnating oil per cent of a per cent solution of sulfuric acid, agitate vigorously with air, allow to settle and draw off the acid solution whereupon the oil may be used for wood impregnation with improved results.

Eifects amounting to an increase of from 100 to 500 per cent in the amount of oil injected into the wood under otherwise equal conditions have been obtained. A -50 Application filed November 30, 1926.. Serial No. 151,838.

mixture of creosote oil and petroleum residuum (a viscous residue of petroleum usually used as fuel) treated by the procedure described, i. e., washed with sulfuric or other acid of any convenient strength, for instance, 30 per cent sulfuric acid, in almost any quan tity, say 0.5 to 5 per cent by volume and up wards, can be made to completely impregnate wood in a much shorter time and at a lower pressure than the untreated mixture.

As has been indicated the treatment of the oily impregnating agent is applicable to such agents generally and is not limited to any particular acid or strength or quantity thereof but the acid preferably used in quantity and concentration insuiiicient to effect refining of the oil or oily impregnating agent.

No definite theory explaining the effect of the acid treatment upon the oily impregnating agent has been determined. The change in the oil as a result of the acid treatment evidently results in a change in the capillarity relations of the oil and the wood whereby the oil more readily wets the wood and more easily forced into its minute pores. Although it appears that the change in the acid ity of the oil produces the change in its penetration properties since washing the oil with alkali has an opposite effect, it has been obi served that no more than a negligible quantity of acid or alkali is retained by the treated oil in either case. The invention is particularly valuable in the treatment of woods which are difficult to impregnate with oily preservative materials, such as fir, spruce, and the like.

The acid treatment of oily wood impregnating agents for the purpose of improving their penetrative properties in accordance with the invention is to be clearly distinguished from the refining of oils, particularly petroleum oils, by acid treatment. The acid treatment ordinarily used for refining oils, for instance the typical treatment with sulfuric acid of about Be, is not applicable for, improving the penetrative properties of wood preserving oils in accordance with the invention and oils which are ordinarily refined by the 60 Be. sulfuric acid treatment are not ordinarily considered as wood preserving oils and the effects of the acid treatments of the two types of oils are different. The refining of mineral oils by means of acid ordinarily requires concen- Ill) trated acid, i. e., 60 Be. sulfuric acid which reacts with certain unstable and reactive constituents of the oil and results in a clarification of the oil and improvement in its odor 1 nd ageing properties, whereas the acid treatment of the invention requires only weak acid of say up to 30 Be. sulfuric acid which does not appreciably react with the unstable and reactive constituents of the oil and does not clarity or deodorize it or improve its ageing properties, i. e., it noes not exert an appreciable refining elicct. Mineral oils which are customarily refined by means of sulfuric acid of about 50 Be. contain only a relatively small amount of unstable and reactive constituents whereas wood preserving oils ordinarily contain a relatively large proportion of unstable and reactive constituents. These unstable and reactive constituents in Wood preserving oils would be removed by strong acid treatment which would involve a prohibitive consumption of acid and woulld leave only a relatively small amount of refined oil which would not be desirable for wood preserving purposes. Thus the acid treatments tor refining oils and for improving their penetrative properties in accordance with the invention. are different, particularly with respect to the kind and concentration of acid used, the oils treated are different, and the desired results and the results actually obtained pregnating against with a solution of a strong mineral acid of a concentration and in quantity insul'licient to effect refining of the oily wood impregnating agent.

3. Process of improving the penetrative properties of oily wood impregnating agents, which comprises contacting an oily wood im pregnating agent with about 5 per cent by volume of a solution of a mineral acid in a concentration insufiicient to effect refining of the oily wood impregnating agent.

at. Process of improving the penetrative properties of oily wood impregnating agents, which comprises contacting the oily wood impregnating agent with about 5 per cent by volume of a 30 per cent solution of sulfuric acid.

5. Process of improving the penetrative properties of oily wood impregnating agents, which comprises agitating the oily Wood impregnating agent with a relatively small proportion of a dilute solution of a strong mineral acid, and separating the acid solution from the oily material.

6. Oily wood impregnating agents obtainable by washing oilv wood preserving materials with acids or a concentration and in quantity insufficient to eliect refining of: the oily wood preserving materials, said agents retaining only negligible quantities of said acids and having penetrative properties at least 100% greater than tne corresponding untreated materials.

7. An oil wood impregnating agent resulting from the treatment of an oily material capable of use for wood impregnation with a relatively small quantity ot a comparatively dilute solution of a strong mineral acid, said agent having penetrative properties at least 100% greater than those of said oily material.

In testimony whereof, I afiiz: my signature.

ARTHUR M. HOlVALD. 

